1. Field of the Invention
The present invention relates to a nonwoven fibrous web, typically referred to herein as a "fabric", which is stretchable and is particularly useful as thermal insulation in active sportswear, such as skiwear and snowmobile suits, and in outdoor work clothes. The fabric, which comprises thermally bondable, thermally coilable bicomponent staple fibers, has low power stretch which is particularly desirable for ease and comfort during wear. The present invention also relates to a process for producing the fabric.
2. Description of the Prior Art
Nonwoven thermal insulating fabrics made of thermally bondable bicomponent fibers are known in the art. Such fabrics are described, for example, in U.S. Pat. No. 4,189,338, U.S. Pat. No. 4,068,036, U.S. Pat. No. 3,589,956 and U.K. Patent Application No. 2,096,048. However, these fabrics do not possess a useful amount of stretch, since there is insufficient springiness in the fibers between points of fiber bonding. In fact, such springiness is deliberately avoided, because the fibers used to produce such fabrics are required to have minimal latent crimp formation during thermal bonding to achieve the desired low density and/or good uniformity. Such reduction of latent crimp has been achieved by fiber stretching (U.S. Pat. No. 4,189,338), by fiber annealing (U.S. Pat. No. 3,589,956), by crimp development prior to forming the nonwoven fabric (U.S. Pat. No. 4,068,036), and by thermal conditioning of the fibers (U.K. Patent Application No. 2,096,048).
Nonwoven thermal insulating fabrics having stretch properties are also known. A non-woven thermal insulating stretch material called "Viwarm" is produced in Japan. The material is a spray-bonded, lightly needle-tacked, nonwoven web of a blend of one and three denier single component polyester fibers, the three denier fibers having sufficient crimp to provide stretch properties. However, the product possesses stretch having undesirably high power for end uses where ease and comfort is particularly desirable and does not have the desired high thermal insulating properties combined with low density desired for optimum performance characteristics. When weight is of primary consideration, as in such insulated articles as skiwear, snowmobile suits, and coats, a relatively dense, heavy product is often found unsatisfactory.
Although a nonwoven product having low-density, high thermal insulating properties and low power, comfort stretch, i.e., a fabric which is easily stretched at low force and recovers to substantially the original dimensions after removal of the force, is desirable, such a product was not available prior to the present invention.
It is, therefore, an object of the present invention to provide a nonwoven stretch fabric having excellent thermal insulating values, low density, and low power, comfort stretch suitable for use in garments.
Another object of the present invention is to provide a nonwoven stretch fabric comprised of thermally bondable, thermally crimpable bicomponent staple fibers.
A further object of the present invention is to provide a nonwoven stretch fabric having substantially uniform thickness, weight, and density.
A still further object of the present invention is to provide a process for producing a highly uniform stretch fabric having excellent thermal insulating values, low density, and low power comfort stretch.